In a vehicle ac generator, electric components such as a rectifying device and a brush device are generally fixed outside of a frame. A protection cover is fixed on the electric components to protect the electric components from foreign materials. The protection cover is formed with air intake openings through which cooling air is sucked in the ac generator with rotation of a rotor for cooling the electric components and a stator winding of a stator. This kind of ac generator is for example disclosed in JP-A-10-56760.
In the ac generator, however, it is likely that foreign materials, such as an erroneously refueled engine oil, oil from a brake fluid, and the drops of cooling water, will enter the inside of the ac generator from the air intake openings. Also, if water enters an engine compartment with dirt splashed by rotating tires and drops on the ac generator, the water will enter in the inside of the ac generator with the flow of cooling air through the air intake openings. If the water adheres to surfaces of metal components in the vehicle ac generator, it will cause the components to rust by oxidation, resulting in abnormal power generation. To restrict the entry of the foreign materials such as oil and water, it is conceived to close the air intake openings. However, if the air intake openings are closed, cooling efficiency is deteriorated. Therefore, it may not be practical in view of a recent high power output trend.
In a vehicle ac generator disclosed in FR2736770A1, a duct member is fixed to a resinous cover so that the opening direction of the air intake openings is changed. Further, a cover member is fixed to the air intake openings to restrict the entry of foreign materials. The duct member has a nail-shaped hook portion to be fixed to the cover. In the ac generator, however, the duct member is a separate part and is fixed to the cover by using the hook structure. Therefore, the number of component parts is increased and the construction of connecting the nail-shaped hook portion is added. As a result, the costs will be largely increased. Further, since the duct member is fixed by using the hook structure, it is difficult to air-tightly seal between the cover and the duct member. Also, if the hook portion is deteriorated, the duct member will be separated from the cover. In addition, a space of an engine compartment has been recently reduced to increase the space for a passenger compartment. Therefore, it is difficult to ensure a space for mounting the ac generator with the large duct member in the engine compartment.